Designing an arena that resolves
The hardest part of an escape video is making it hard without making it impossible. The variables that decide solvability are gap size, ring speed, and ball speed, and they interact in a way that is easier to feel than to calculate. The reliable method is to start solvable and tighten: build the arena with a generous gap, confirm the ball escapes, then reduce the gap in small steps until near misses appear.
Opposite Gaps is the safety valve. With two openings per ring the ball has twice the chance of alignment at any moment, so you can run gaps narrow enough to look impossible while keeping the run winnable. Gap Support and Side Guards work the other way, deflecting a ball that grazes the edge back into the arena, which produces more near misses without changing the geometry.

